The present invention generally relates to apparatus and method for separating debris from a liquid stream, and more specifically, to a centrifugal debris trap useful to remove abrasive debris from a lubricating oil in an engine.
During manufacture and/or repair of an engine or other components, various forms of debris, referred to as build-related debris, may be inadvertently incorporated therein. The types of debris may include abrasive materials such as metal shavings, dust, casting sand, and the like. Build related and other types of debris may be difficult to control and remove, in that they may remain within passages and conduits of various engine components in spite of attempts which may be made to remove such materials prior to engine startup.
In an example, debris may be located downstream of a filtration system. Such debris may potentially damage parts which may be critical to engine operation prior to the debris being caught by the filtration system. For example, debris located after a filtration system but prior to main shaft rotor bearings in, for example, a gas turbine, may result in a failed main shaft rotor bearing, which may result in destruction of an entire engine rotor group and/or destruction of various components such as a stator/shroud structure integral to an engine. Bearing and other damage which may be caused by build-related debris may thus be considered a major source of premature bearing failure, and may also result in increased maintenance costs, warranty costs, and the like.
Debris may also be formed from various parts of an engine wearing during use. As with build-related debris, this debris may be difficult to control as it may be present after a filtration system but prior to, for example, a component requiring lubrication such as a bearing. Such debris may also result in damage to a component and/or failure of an engine or system.
Taking as an example, FIG. 1 shows a cross-sectional plan view of a rotating shaft oil lubrication system, generally referred to as 210, which may be representative of a system that may not provide for removal of debris post a filtration system (not shown). In system 210, a fluid 212 may be distributed to one or more bearing assemblies which may include one or more bearings 214a, 214b, 214c, 214d via a plurality of conduits 216, 232, 234, 236, and 238. As shown, fluid 212 may travel along a flow path 226 and/or along a flow path 228 thorough a rotating spline shaft 218 into a rotating chamber 220, all of which may be rotating along a center axis 222 at a rotational speed 240. The centrifugal force 224 acting on fluid 212 may propel fluid 212 through the plurality of conduits 216, 232, 234, 236 and 238 such that fluid 212 may contact bearings 214a–d thus providing lubrication thereto. Accordingly, any debris 230 which may be disposed within flow path 226 and/or flow path 228, or oil supply passages (not shown) that feed oil to rotating spline shaft 218, may come in contact with bearings 214a, 214b, 214c, and/or 214d, which may lead to damage of bearings 214a–d, and/or other parts of system 210.
Various attempts at removing debris from engines include U.S. Pat. No. 3,478,887, which is directed to a combination centrifugal and magnetic separation device. The separator device disclosed therein may include a cylindrical housing mounted in a slide valve for rotation therewith. The housing may be provided with end faces with an inlet aperture and an outlet aperture disposed as a plurality of openings angularly spaced on a circle circumferentially of an axis of rotation of the separator device. Each of the housing parts may have a respective inwardly directed axial pin portion between which an annular magnet may be disposed circumferentially thereof projecting into a contaminant separating chamber defined by a housing. During operation, ferromagnetic particles may be separated from a fluid flow by collecting on a surface of a magnet, while other solid contaminants, which may not be magnetic, may be separated by centrifugal action. Contaminants collect on the inner wall of the housing defining an outer circumference of the separating chamber.
Unlike the present invention, the separation device disclosed in the reference may require a slide valve, a commutating valve arrangement, or the like for operation. If such an arrangement is not present on a system, it may need to be incorporated into the design of the device, or may require the separator being located external to a component being protected, both of which may add complexity to a system. Furthermore, the flow path of the device shown in the reference may have an inlet and a separate outlet, which may be essentially in-line with one another. Under certain conditions which may include relatively high flow rates as determined relative to the separation device, the liquid may flow essentially straight through the separator described by the reference without any centrifugal filtration. Thus, efficiency of the prior art separator device may depend on the flow rate of the liquid passing through the device.
U.S. Pat. No. 6,484,847 is directed to a hermetic compressor assembly, comprising a pivoting magnetic member in fluid communication with a liquid lubricant, wherein at least a portion of any ferrous particles contained in a liquid lubricant may be attracted to, and may be retained by, the magnetic member. While the magnetic member may retain a portion of the ferrous particles present, the magnetic member may not address removal of non-ferrous materials such as casting sand and other abrasive materials as described above. Furthermore, the flow of the liquid lubricant may be essentially straight through the magnetic member shown. Accordingly, the efficiency of the separation of debris from a liquid flowing through the device may be dependent on an amount of communication the fluid may have with the magnetic member. The more surface area the magnetic member may have, the more communication between the fluid and the magnetic member that may result. Should such space not be available within a system or engine in which such a magnetic member is to be located, the magnetic member may require additional systems or space to be accommodated, which may add complexity to the system.
As can be seen, there is a need for apparatus and method of trapping build related and other types of both ferrous and non-ferrous debris that may be located in, for example a lubrication fluid which may be between a filtration system and a component to be lubricated therewith. There is also a need for apparatus and method of trapping build related and other types of debris which may not have a flow path between a separate inlet and outlet, and may thus provide for debris separation which is not substantially affected by the rate at which a fluid flows through the debris apparatus. Moreover, there is a need for apparatus and method of trapping build related and other types of debris which is integral to the device or system such that it does not add appreciable complexity to a system in which it is located.